The project is examining: 1. The utility of EEG measures in differentiating between normal children and those with Attention-Deficit Hyperactivity Disorder (ADHD); 2. The EEG correlates of psychostimulant response among children with ADHD; 3. The association between risk alleles of several dopamine genes (D2, D4, and DAT) to EEG measures among children with ADHD.